Preeclampsia is a pregnancy complication characterized by high blood pressure and signs of damage to another organ system, often the kidneys. Preeclampsia usually begins after 20 weeks of pregnancy in a woman whose blood pressure had been normal. Even a slight rise in blood pressure may be a sign of preeclampsia.

Left untreated, preeclampsia can lead to serious — even fatal — complications for both you and your baby. If you have preeclampsia, the only cure is delivery of your baby.

If you're diagnosed with preeclampsia too early in your pregnancy to deliver your baby, you and your doctor face a challenging task. Your baby needs more time to mature, but you need to avoid putting yourself or your baby at risk of serious complications.

Preeclampsia sometimes develops without any symptoms. High blood pressure may develop slowly, but more commonly it has a sudden onset. Monitoring your blood pressure is an important part of prenatal care because the first sign of preeclampsia is commonly a rise in blood pressure. Blood pressure that is 140/90 millimeters of mercury (mm Hg) or greater — documented on two occasions, at least four hours apart — is abnormal.

Changes in vision, including temporary loss of vision, blurred vision or light sensitivity

Upper abdominal pain, usually under your ribs on the right side

Nausea or vomiting

Decreased urine output

Decreased levels of platelets in your blood (thrombocytopenia)

Impaired liver function

Shortness of breath, caused by fluid in your lungs

Sudden weight gain and swelling (edema) — particularly in your face and hands — often accompanies preeclampsia. But these things also occur in many normal pregnancies, so they're not considered reliable signs of preeclampsia.

When to see a doctor

Make sure you attend your prenatal visits so that your care provider can monitor your blood pressure. Contact your doctor immediately or go to an emergency room if you have severe headaches, blurred vision, severe pain in your abdomen or severe shortness of breath.

Because headaches, nausea, and aches and pains are common pregnancy complaints, it's difficult to know when new symptoms are simply part of being pregnant and when they may indicate a serious problem — especially if it's your first pregnancy. If you're concerned about your symptoms, contact your doctor.

The exact cause of preeclampsia is unknown. Experts believe it begins in the placenta — the organ that nourishes the fetus throughout pregnancy. Early in pregnancy, new blood vessels develop and evolve to efficiently send blood to the placenta. In women with preeclampsia, these blood vessels don't seem to develop properly. They're narrower than normal blood vessels and react differently to hormonal signaling, which limits the amount of blood that can flow through them.

Causes of this abnormal development may include:

Insufficient blood flow to the uterus

Damage to the blood vessels

A problem with the immune system

Certain genes

Other high blood pressure disorders during pregnancy

Preeclampsia is classified as one of four high blood pressure disorders that can occur during pregnancy. The other three are:

Gestational hypertension. Women with gestational hypertension have high blood pressure but no excess protein in their urine or other signs of organ damage. Some women with gestational hypertension eventually develop preeclampsia.

Chronic hypertension. Chronic hypertension is high blood pressure that was present before pregnancy or that occurs before 20 weeks of pregnancy. But because high blood pressure usually doesn't have symptoms, it may be hard to determine when it began.

Chronic hypertension with superimposed preeclampsia. This condition occurs in women who have chronic high blood pressure before pregnancy who then develop worsening high blood pressure and protein in the urine or other health complications during pregnancy.

Preeclampsia develops only as a complication of pregnancy. Risk factors include:

History of preeclampsia. A personal or family history of preeclampsia significantly raises your risk of preeclampsia.

First pregnancy. The risk of developing preeclampsia is highest during your first pregnancy.

New paternity. Each pregnancy with a new partner increases the risk of preeclampsia over a second or third pregnancy with the same partner.

Age. The risk of preeclampsia is higher for pregnant women older than 40.

Obesity. The risk of preeclampsia is higher if you're obese.

Multiple pregnancy. Preeclampsia is more common in women who are carrying twins, triplets or other multiples.

Interval between pregnancies. Having babies less than two years or more than 10 years apart leads to a higher risk of preeclampsia.

History of certain conditions. Having certain conditions before you become pregnant — such as chronic high blood pressure, migraine headaches, type 1 or type 2 diabetes, kidney disease, a tendency to develop blood clots, or lupus — increases your risk of preeclampsia.

The more severe your preeclampsia and the earlier it occurs in your pregnancy, the greater the risks for you and your baby. Preeclampsia may require induced labor and delivery. Surgical delivery (cesarean section or C-section) isn't always advantageous unless other problems are present, such as a baby in breech presentation, or if a speedy delivery is necessary. If you have severe preeclampsia or you're at less than 30 weeks gestation, a C-section may be necessary.

Complications of preeclampsia may include:

Lack of blood flow to the placenta. Preeclampsia affects the arteries carrying blood to the placenta. If the placenta doesn't get enough blood, your baby may receive less oxygen and fewer nutrients. This can lead to slow growth, low birth weight or preterm birth. Prematurity can lead to breathing problems for the baby.

Placental abruption. Preeclampsia increases your risk of placental abruption, in which the placenta separates from the inner wall of your uterus before delivery. Severe abruption can cause heavy bleeding and damage to the placenta, which can be life-threatening for both you and your baby.

HELLP syndrome. HELLP — which stands for hemolysis (the destruction of red blood cells), elevated liver enzymes and low platelet count — syndrome can rapidly become life-threatening for both you and your baby. Symptoms of HELLP syndrome include nausea and vomiting, headache, and upper right abdominal pain. HELLP syndrome is particularly dangerous because it represents damage to several organ systems. On occasion, it may develop suddenly, even before high blood pressure is detected.

Eclampsia. When preeclampsia isn't controlled, eclampsia — which is essentially preeclampsia plus seizures — can develop. Symptoms that suggest imminent eclampsia include upper right abdominal pain, severe headache, vision problems and change in mental status, such as decreased alertness. Because eclampsia can have serious consequences for both mom and baby, delivery becomes necessary, regardless of how far along the pregnancy is.

Cardiovascular disease. Having preeclampsia may increase your risk of future heart and blood vessel (cardiovascular) disease. The risk is even greater if you've had preeclampsia more than once or you've had a preterm delivery. To minimize this risk, after delivery try to maintain your ideal weight, eat a variety of fruits and vegetables, exercise regularly, and don't smoke.

Preeclampsia will probably be diagnosed during a routine prenatal exam. After that, you'll likely have additional visits with your obstetrician.

Here's some information to help you get ready for your appointment, and what to expect from your doctor.

What you can do

To prepare for your appointment:

Write down any symptoms you're experiencing, even if you think they're normal pregnancy symptoms.

Make a list of all medications, vitamins and supplements that you're taking.

Take a family member or friend along, if possible, to help you remember all of the information provided during your appointment.

Write down questions to ask your doctor, listing them in order of importance in case time runs out.

For preeclampsia, some basic questions to ask your doctor include:

Has the condition affected my baby?

Is it safe to continue the pregnancy?

What are the signs I need to look out for, and when should I call you?

How often do you need to see me? How will you monitor my baby's health?

What treatments are available, and which do you recommend for me?

I have other health conditions. How can I best manage these conditions together?

Do I need to follow any activity restrictions?

Will I need a C-section?

Do you have any brochures or other printed material that I can have? What websites do you recommend?

In addition to the questions that you've prepared, don't hesitate to ask questions that occur to you during your appointment.

What to expect from your doctor

Questions your doctor may ask include:

Is this your first pregnancy or your first pregnancy with this baby's father?

Have you had any unusual symptoms lately, such as blurred vision or headaches?

Do you ever feel pain in your upper abdomen that seems unrelated to your baby's movements?

Have you had high blood pressure in the past?

Did you experience preeclampsia with any previous pregnancies?

Have you had complications during a previous pregnancy?

What other health conditions are you dealing with?

To diagnose preeclampsia, you have to have high blood pressure and one or more of the following complications after the 20th week of pregnancy:

Protein in your urine (proteinuria)

A low platelet count

Impaired liver function

Signs of kidney trouble other than protein in the urine

Fluid in the lungs (pulmonary edema)

New-onset headaches

Visual disturbances

Previously, preeclampsia was only diagnosed if a pregnant woman had high blood pressure and protein in her urine. However, experts now know that it's possible to have preeclampsia, yet never have protein in the urine.

A blood pressure reading in excess of 140/90 mm Hg is abnormal in pregnancy. However, a single high blood pressure reading doesn't mean you have preeclampsia. If you have one reading in the abnormal range — or a reading that's substantially higher than your usual blood pressure — your doctor will closely observe your numbers. Having a second abnormal blood pressure reading four hours after the first may confirm your doctor's suspicion of preeclampsia. Your doctor may have you come in for additional blood pressure readings and blood and urine tests.

Tests that may be needed

Blood tests. These can determine how well your liver and kidneys are functioning and whether your blood has a normal number of platelets — the cells that help blood clot.

Urine analysis. A single urine sample that measures the ratio of protein to creatinine — a chemical that's always present in the urine — may be used to make the diagnosis. Urine samples taken over 24 hours can quantify how much protein is being lost in the urine, an indication of the severity of preeclampsia.

Fetal ultrasound. Your doctor may also recommend close monitoring of your baby's growth, typically through ultrasound. The images of your baby created during the ultrasound exam allow your doctor to estimate fetal weight and the amount of fluid in the uterus (amniotic fluid).

Nonstress test or biophysical profile. A nonstress test is a simple procedure that checks how your baby's heart rate reacts when your baby moves. A biophysical profile combines an ultrasound with a nonstress test to provide more information about your baby's breathing, tone, movement and the volume of amniotic fluid in your uterus.

The only cure for preeclampsia is delivery. You're at increased risk of seizures, placental abruption, stroke and possibly severe bleeding until your blood pressure decreases. Of course, if it's too early in your pregnancy, delivery may not be the best thing for your baby.

If you're diagnosed with preeclampsia, your doctor will let you know how often you'll need to come in for prenatal visits — likely more frequently than what's typically recommended for pregnancy. You'll also need more-frequent blood tests, ultrasounds and nonstress tests than would be expected in an uncomplicated pregnancy.

Medications

Possible treatment for preeclampsia may include:

Medications to lower blood pressure. These medications, called antihypertensives, are used to lower your blood pressure if it's dangerously high. Blood pressure in the 140/90 millimeters of mercury (mm Hg) range generally isn't treated. Although there are many different types of antihypertensive medications, a number of them aren't safe to use during pregnancy. Discuss with your doctor whether you need to use an antihypertensive medicine in your situation to control your blood pressure.

Corticosteroids. If you have severe preeclampsia or HELLP syndrome, corticosteroid medications can temporarily improve liver and platelet function to help prolong your pregnancy. Corticosteroids can also help your baby's lungs become more mature in as little as 48 hours — an important step in preparing a premature baby for life outside the womb.

Anticonvulsant medications. If your preeclampsia is severe, your doctor may prescribe an anticonvulsant medication, such as magnesium sulfate, to prevent a first seizure.

Bed rest

Bed rest used to be routinely recommended for women with preeclampsia. But research hasn't shown a benefit from this practice, and it can increase your risk of blood clots, as well as impact your economic and social lives. For most women, bed rest is no longer recommended.

Hospitalization

Severe preeclampsia may require that you be hospitalized. In the hospital, your doctor may perform regular nonstress tests or biophysical profiles to monitor your baby's well-being and measure the volume of amniotic fluid. A lack of amniotic fluid is a sign of poor blood supply to the baby.

Delivery

If you're diagnosed with preeclampsia near the end of your pregnancy, your doctor may recommend inducing labor right away. The readiness of your cervix — whether it's beginning to open (dilate), thin (efface) and soften (ripen) — also may be a factor in determining whether or when labor will be induced.

In severe cases, it may not be possible to consider your baby's gestational age or the readiness of your cervix. If it's not possible to wait, your doctor may induce labor or schedule a C-section right away. During delivery, you may be given magnesium sulfate intravenously to prevent seizures.

After delivery, expect your blood pressure to return to normal within 12 weeks but usually much sooner. If you need pain-relieving medication after your delivery, ask your doctor what you should take. Nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen (Advil, Motrin IB, others) and naproxen sodium (Aleve), can increase your blood pressure. Acetaminophen (Tylenol, others) is usually a safe alternative.

Discovering that you have a potentially serious pregnancy complication can be frightening. If you're diagnosed with preeclampsia late in your pregnancy, you may be surprised and scared to know that you'll be induced right away. If you're diagnosed earlier in your pregnancy, you may have many weeks to worry about your baby's health.

It may help to learn about your condition. In addition to talking to your doctor, do some research. Make sure you understand when to call your doctor, how you should monitor your baby and your condition, and then find something else to occupy your time so that you don't spend too much time worrying.

Researchers continue to study ways to prevent preeclampsia, but so far, no clear strategies have emerged. Eating less salt, changing your activities, restricting calories, or consuming garlic or fish oil doesn't reduce your risk. Increasing your intake of vitamins C and E hasn't been shown to have a benefit, and the research into vitamin D is ongoing.

In certain cases, however, you may be able to reduce your risk of preeclampsia with:

Low-dose aspirin. If you had preeclampsia in a previous pregnancy that resulted in delivery before 34 weeks' gestation or you had preeclampsia in more than one previous pregnancy, your doctor may recommend a daily low-dose aspirin — between 60 and 81 milligrams — beginning late in your first trimester.

Calcium supplements. In some populations, women who have calcium deficiency before pregnancy — and who don't get enough calcium during pregnancy through their diets — might benefit from calcium supplements to prevent preeclampsia. However, it's unlikely that women from the United States or other developed countries would have calcium deficiency to the degree that calcium supplements would benefit them.

It's important that you don't take any medications, vitamins or supplements without first talking to your doctor.

Before you become pregnant, especially if you've had preeclampsia before, it's a good idea to be as healthy as you can be. Lose weight if you need to, and make sure other conditions, such as diabetes, are well-managed.

Once you're pregnant, take care of yourself — and your baby — through early and regular prenatal care. If preeclampsia is detected early, you and your doctor can work together to prevent complications and make the best choices for you and your baby.

Bushnell C, et al. Guidelines for the prevention of stroke in women: A statement for healthcare professionals from the American Heart Association/American Stroke Association. Stroke. In press. Accessed Feb. 10, 2014.

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